How To Use CPT Code 81335

CPT 81335 describes the genetic analysis procedure for detecting specific changes in the thiopurine S-methyltransferase (TPMT) gene, specifically for common variants such as *2 and *3. This article will cover the description, procedure, qualifying circumstances, appropriate usage, documentation requirements, billing guidelines, historical information, similar codes and billing examples.

1. What is CPT Code 81335?

CPT 81335 can be used to describe the genetic analysis procedure performed to detect specific changes in the TPMT gene, specifically for common variants such as *2 and *3. This code is used when the lab analyst performs the technical steps involved in extracting nucleic acids, amplifying the gene, and detecting the target genes using a specimen such as blood.

2. Official Description

The official description of CPT code 81335 is: ‘TPMT (thiopurine S-methyltransferase) (eg, drug metabolism), gene analysis, common variants (eg, *2, *3).’

3. Procedure

1. The lab analyst performs the technical steps involved in the genetic analysis procedure for detecting specific changes in the TPMT gene.
2. This includes extracting nucleic acids from a specimen, such as blood, using methods like digestion and cell lysis.
3. The lab analyst then amplifies the gene, making more copies of the desired gene for study, using processes like polymerase chain reaction (PCR) or transcription of DNA to RNA and reverse transcription from RNA to make an additional copy of the DNA.
4. Finally, the lab analyst detects the target genes, such as common variants of the TPMT gene (*2, *3), using methods like nucleic acid probes.

4. Qualifying circumstances

CPT 81335 is typically ordered by clinicians for patients with specific conditions or situations. This genetic analysis procedure can be useful for organ transplant recipients, patients with acute lymphoblastic leukemia (ALL), and individuals with autoimmune disorders like rheumatoid arthritis and Crohn’s disease. It helps predict potential toxicity of anti-metabolite thiopurine drugs.

5. When to use CPT code 81335

CPT code 81335 should be used when the lab analyst performs the genetic analysis procedure to detect specific changes in the TPMT gene, specifically for common variants such as *2 and *3. It is important to note that this code should not be used for testing a specific condition but rather for predicting potential drug toxicity.

6. Documentation requirements

To support a claim for CPT 81335, the documentation should include:

• Reason for ordering the genetic analysis procedure
• Details of the specific changes in the TPMT gene being tested
• Date and time of the procedure
• Results of the analysis, including the presence or absence of common variants (*2, *3)
• Signature of the lab analyst performing the procedure

7. Billing guidelines

When billing for CPT 81335, ensure that the genetic analysis procedure is performed by a qualified lab analyst. It is important to note that some payers may separately reimburse for specimen collection using a different code, such as 36415. Additionally, if the ordering clinician requests physician interpretation of the test and the pathologist provides an interpretation and writes a report, you may report G0452 with modifier 26 to Medicare and other payers.

8. Historical information

CPT 81335 was added to the Current Procedural Terminology system on January 1, 2018. There have been no updates to the code since its addition.

9. Examples

1. A lab analyst performs the genetic analysis procedure to detect specific changes in the TPMT gene for common variants (*2, *3) in a patient with rheumatoid arthritis who is starting anti-metabolite thiopurine drug therapy.
2. For an organ transplant recipient, the lab analyst performs the genetic analysis procedure to predict potential toxicity of anti-metabolite thiopurine drugs by detecting specific changes in the TPMT gene for common variants (*2, *3).
3. In a patient with acute lymphoblastic leukemia (ALL), the lab analyst performs the genetic analysis procedure to determine the presence of common variants (*2, *3) in the TPMT gene, helping to guide the choice of anti-metabolite thiopurine drugs.
4. A lab analyst performs the genetic analysis procedure to detect specific changes in the TPMT gene for common variants (*2, *3) in a patient with Crohn’s disease who is being considered for anti-metabolite thiopurine drug therapy.
5. For a patient with a history of adverse reactions to anti-metabolite thiopurine drugs, the lab analyst performs the genetic analysis procedure to detect specific changes in the TPMT gene for common variants (*2, *3) to help predict potential drug toxicity.